Can we teach an artificial intelligence through sentences?
I think that what you're really asking about is the question of knowledge representation.  Regardless of how you train your AI, one of the most fundamental questions is how do you represent "knowledge" and especially when it exists at different levels of abstraction, may be mutually recursive, etc.  Along with that goes the question of belief revision which deals with how you update existing beliefs/knowledge in the light of new information.

Both of these areas are still subject to plenty of active research and neither has entirely settled answers to the core questions.  But progress has been made in both areas.  

Personally I suspect that something like semantic networks or conceptual graphs will be the best answer to the KR problem.  Dealing with belief revision seems even fuzzier to me, although there are known strategies (like the AGM postulates) that work to a point. Something like Bayesian Belief Networks may also prove useful.